This invention relates to a reversible rotary actuator having an electric motor which is selectively operable to rotate an output shaft in one direction. During driving of the output shaft by the motor, a torsion spring is wound so as to store energy for rotating the shaft in the other direction when the motor is de-energized and the spring unwinds.
More particularly, the invention relates to a rotary actuator of the type in which the motor rotates the output shaft and winds the spring by way of a gear train which substantially reduces the speed and substantially amplifies the torque of the motor. When the spring unwinds to rotate the output shaft, the spring acts reversely through the gear train and backdrives the motor shaft.
In most prior actuators of the foregoing type, the return spring has acted either directly on the output shaft or on the final drive train gear attached to the drive shaft.